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<?php
namespace ParagonIE\ConstantTime;
/**
* Copyright (c) 2016 - 2017 Paragon Initiative Enterprises.
* Copyright (c) 2014 Steve "Sc00bz" Thomas (steve at tobtu dot com)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
/**
* Class Hex
* @package ParagonIE\ConstantTime
*/
abstract class Hex implements EncoderInterface
{
/**
* Convert a binary string into a hexadecimal string without cache-timing
* leaks
*
* @param string $bin_string (raw binary)
* @return string
*/
public static function encode($bin_string)
{
$hex = '';
$len = Binary::safeStrlen($bin_string);
for ($i = 0; $i < $len; ++$i) {
$chunk = \unpack('C', Binary::safeSubstr($bin_string, $i, 2));
$c = $chunk[1] & 0xf;
$b = $chunk[1] >> 4;
$hex .= pack(
'CC',
(87 + $b + ((($b - 10) >> 8) & ~38)),
(87 + $c + ((($c - 10) >> 8) & ~38))
);
}
return $hex;
}
/**
* Convert a binary string into a hexadecimal string without cache-timing
* leaks, returning uppercase letters (as per RFC 4648)
*
* @param string $bin_string (raw binary)
* @return string
*/
public static function encodeUpper($bin_string)
{
$hex = '';
$len = Binary::safeStrlen($bin_string);
for ($i = 0; $i < $len; ++$i) {
$chunk = \unpack('C', Binary::safeSubstr($bin_string, $i, 2));
$c = $chunk[1] & 0xf;
$b = $chunk[1] >> 4;
$hex .= pack(
'CC',
(55 + $b + ((($b - 10) >> 8) & ~6)),
(55 + $c + ((($c - 10) >> 8) & ~6))
);
}
return $hex;
}
/**
* Convert a hexadecimal string into a binary string without cache-timing
* leaks
*
* @param string $hex_string
* @return string (raw binary)
* @throws \RangeException
*/
public static function decode($hex_string)
{
$hex_pos = 0;
$bin = '';
$c_acc = 0;
$hex_len = Binary::safeStrlen($hex_string);
$state = 0;
if (($hex_len & 1) !== 0) {
throw new \RangeException(
'Expected an even number of hexadecimal characters'
);
}
$chunk = \unpack('C*', $hex_string);
while ($hex_pos < $hex_len) {
++$hex_pos;
$c = $chunk[$hex_pos];
$c_num = $c ^ 48;
$c_num0 = ($c_num - 10) >> 8;
$c_alpha = ($c & ~32) - 55;
$c_alpha0 = (($c_alpha - 10) ^ ($c_alpha - 16)) >> 8;
if (($c_num0 | $c_alpha0) === 0) {
throw new \RangeException(
'hexEncode() only expects hexadecimal characters'
);
}
$c_val = ($c_num0 & $c_num) | ($c_alpha & $c_alpha0);
if ($state === 0) {
$c_acc = $c_val * 16;
} else {
$bin .= \pack('C', $c_acc | $c_val);
}
$state ^= 1;
}
return $bin;
}
}
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